I just went through this with 5 - 3tb drives. I had just enough space to move data off of drive3 onto another drive without having to upgrade to 1 bigger drive or adding a drive.
round [source] [dest]
------- ----------- --------
1 disk3 disk4
Disk3 is new XFS disk
2 disk1 disk3
Disk1 is new XFS disk
3 disk2 disk1
Disk2 is new XFS disk
4 disk4 disk2
Disk4 is new XFS disk
In progress.....Move Disk3 files from step one to empty disk4
Still need to do...
Verify shares and excluded disks - don't think I set any up.
Look at backup cron jobs and change where those point to.
Power back up Plex docker make sure everything looks right.
Change location for music in LMS.
2. Do I replace the parity drive first?
Yes if you add the other 6tb drive as data. Also run parity check with new disk.
3. To get started how many drives should I buy? I was thinking 2 (1 for Parity, 1 for Data)
That would be a good starting point
5. Should I move all 5TB worth of Data onto the new 6TB Drive or just replace one 2TB drive at a time? My thought is if I move all the Data to the new drive then I can go back and reformat the older drives to XFS and hopefully get a working Mover again!
You could but you may want to do it like below when you move the files.
rsync -avPX /mnt/disk1/ /mnt/disk6/disk1_RFS
rsync -avPX /mnt/disk2/ /mnt/disk6/disk2_RFS
rsync -avPX /mnt/disk3/ /mnt/disk6/disk3_RFS
rsync -avPX /mnt/disk4/ /mnt/disk6/disk4_RFS
That way you can move that back to the drives they were on.
rsync -avPX /mnt/disk6/disk1_RFS/ /mnt/disk1 to move data back to disk1 after formatted to XFS.
6. Any words of advice, hard lessons learned, or oh crap moments you want to share?
Make notes of your current system. Take screen shots if needed. Make a cheat sheet of your steps so you don't miss one.